The paradigm of an extracellular adhesion, fibronectin, interacting with a transmembrane receptor has proven applicable to a number of adhesion systems. There are several other extracellular glycoproteins with biological properties like fibronectin, laminin, thrombospondin, von Willebrand factor, fibrinogen/fibrin, vitronectin, and cytotactin/tenascin/hexabrachion. The structures of each of these proteins either are or very soon will be determined, opening up new possibilities for studies of function. In parallel has come the realization that the transmembrane receptor for fibronectin is only one member of the integrin family of functionally related, homologous, cell adhesion receptors. Fibronectin and related macromolecules are involved in many basic functions of cells, including cell adhesion, determination of cell shape and differentiation, cell migration, cytoskeletal organization, and organization of extracellular matrix. Thus, fibronectin and the molecules with which it interacts are important in embryogenesis, connective tissue organization, hemostasis, thrombosis, wound healing, development of immunity, hemopoiesis, malignant transformation, and tumor metastasis. The challenges to the field over the next several years are to comprehend and organize the large amount of new structural information and design experiments based upon it; learn the relative biological importance of the several seemingly redundant systems; and apply the new insights to the treatment of human diseases. The 1991 Gordon Research Conference will serve as a valuable forum to present and discuss new information, identify problem areas, and plan new approaches.